With a recent commit, Sequel can now set the transaction isolation level used for database transactions. Setting the transaction isolation level is a fairly advanced feature that I don’t expect many people to need, but in some cases it is necessary to get the desired behavior.
The API for setting the transaction isolation level is simple. You use the :isolation option to Database#transaction with either :uncommitted (for READ UNCOMMITTED), :committed (for READ COMMITTED), :repeatable (for REPEATABLE READ), or :serializable (for SERIALIZABLE). A simple example is:
DB.transaction(:isolation=>:serializable) do ... end
You can also set a default isolation level used for transactions via:
DB.transaction_isolation_level = :repeatable
Sequel currently supports setting the transaction isolation level on PostgreSQL, MySQL, and Microsoft SQL Server. Support for other databases may be added in the future.